The present invention is related to cooling of electronic equipment, and more particularly to the use of spray evaporative cooling to cool electronics components.
The demand for higher performance supercomputers continues to create challenging thermal and packaging design environments for today""s computer packaging engineers. As the performance of CRAY supercomputers continues to grow exponentially, in general agreement with Moore""s law (Bar-Cohen, et al, 1988), the thermal and packaging solutions continue to become more complex.
The increase of supercomputer performance over the last 30 years was initially achieved with an increase in the complexity of the computer""s CPU by increasing the number of ICs within a CPU. The next step in performance was achieved by adding more gates per IC along with increasing the clock rate. Performance was further increased by the paralleling of CPUs and then the scaling of groups of CPUs. Now in order to continue on the path of Moore""s law, we are again pushing the IC technology and ultimately the performance of each individual CPU. Die sizes are increasing, and power levels of these devices are increasing at rates approaching that of Moore""s law for supercomputer performance.
One technology that hasn""t been able to keep pace with the ICs is the printed circuit board (PCB) technology. The demands for component placement and IC net routings have exceeded the current state of the art in PCB technology.
One solution to this problem implements a multi-chip module with thin film routing layers (MCM-D) for the packaging of these high performance chip sets. This high density packaging design is, however, capable of producing heat fluxes on the ICs and MCM that approach values of 50 and 15 W/cm2, respectively. The control of the IC""s junction temperature is important for its reliability and for the performance of two communicating devices. The amount of induced leakage xe2x80x9cnoisexe2x80x9d that exists on an integrated circuit is also a function of its temperature.
A number of cooling methodologies have been described by Bar-Cohen (Bar-Cohen, A., xe2x80x9cThermal Management of Electronic Components with Dielectric Liquidsxe2x80x9d, JSME International Journal, Series B, vol. 36, No1,1993), by Simons (Simons, R. E., xe2x80x9cBibliography of Heat Transfer in Electronic Equipmentxe2x80x9d, 1989, IBM Corporation), by Incropera (Incropera, F. P., xe2x80x9cConvection Heat Transfer in Electronic Equipment Coolingxe2x80x9d, Journal of Heat Transfer, Nov. 1988, Vol. 110/1097) and by Bergles (Bergles, A. E., xe2x80x9cLiquid Cooling for Electronic Equipmentxe2x80x9d, International Symposium on Cooling Technology for Electronic Equipment, March 1987). Studies by Chu and Chrysler (Chu, R. C., and Chrysler, G. M., xe2x80x9cElectronic Module Coolability Analysisxe2x80x9d, EEP-Vol. 19-2, Advances in Electronic Packaging-1997 Volume 2, ASME 1997) and by Nakayama (Nakayama, W., xe2x80x9cLiquid-Cooling of Electronic Equipment: Where Does It Offer Viable Solutions?xe2x80x9d, EEP-Vol. 19-2, Advances in Electronic Packaging-1997 Volume 2, ASME 1997), however, indicate that these approaches are no longer capable of satisfying today""s high density packaging requirements (Chu and Chrysler, 1997), (Nakayama, 1997).
As heat flux continues to increase, the most promising methods are those that utilize direct liquid cooling with dielectric fluids. Direct liquid cooling circumvents the problems of high thermal interface resistance associated with conventional technologies and is capable of providing very high heat transfer rates (Bar-Cohen, 1993). A number of such direct liquid cooling techniques are described in, xe2x80x9cThermal Management of Multichip Modules with Evaporative Spray Cooling,xe2x80x9d by G. W. Pautsch and A. Bar-Cohen, published in ASME Advances in Electronic Packaging 1999, EEP-Vol.26-2, 1453-1463, the discussion of which is incorporated herein by reference. That paper concluded that the method of choice for cooling high heat flux electronic components is described as xe2x80x9cHigh Density, Pressure-Atomized Evaporative Spray Coolingxe2x80x9d. This condition occurs when a fluid is sprayed on a surface at a rate that maintains a continuously wetted surface, whose temperature is less than 25xc2x0 C. above the saturation temperature of the thermal coolant. This method, with the selection of an appropriate fluid, such as Fluorinert(trademark) FC-72 which has a boiling point of 56xc2x0 C. at standard atmospheric conditions, allows one to maintain high heat flux components at operating temperatures below 85xc2x0 C.
Each of the above cooling approaches has its deficiencies. What is needed is a system and method for cooling electronics components that addresses these deficiencies.
To address the problems stated above, and to solve other problems which will become apparent in reading the specification and claims, a system and method for cooling electronic components is described. A liquid is heated to a temperature near its boiling point and directed against electronic components such that a portion of the heated liquid vaporizes, forming a mixed phase fluid. The mixed phase fluid is drawn away from the electronic components and the vapor is condensed back into a liquid.
According to another aspect of the present invention, an enclosure includes a plurality of electronics components, cooling means for cooling a gas and distribution means for directing the gas across the electronics components and the cooling means. The distribution means forms a closed system limiting the transfer of the gas both into and out of the distribution means.